Killing multiple bosses at the same time yields no loot whatsoever

This problem is persisting for over a month now. None of the new patches addressed it. Just spent 30 min opening "Sealed Vault" only to find out again that the twins drop no loot, couse my dots killed them at the same time.

It happens with the double Witches and Millers too and it's a nasty bug. Why is this issue being neglected for so long?